In general construction machines, when a work load increases, a pump pressure rises and the delivery flow rate of the pump decreases. As a result, during the time when a front work implement is operated, the speed of the front work implement is lower as the work load is higher.
On the other hand, there is a construction machine in which the aperture area of an operation valve is varied by pressure compensating means in accordance with a differential pressure across the operation valve and an operation amount (see, for example, Patent Document 1). In this construction machine, for example in the case of a swing and boom raising operation for simultaneously performing swinging and boom raising, if boom load is high, the aperture area of an operation valve corresponding to the swing operation is reduced whereas the aperture area of an operation valve corresponding to the boom is increased, whereby an operability similar to that when boom load is low is secured.